InteractionOutput.value() throws an error for Actions with no output DataSchema

[FadySalama]

I encountered this problem while interacting with the TestThing. When invoking the "void-void" action, the action results in an 505: Internal Server Error with the message No schema defined. This is thrown inside value() as seen below:

node-wot/packages/examples/src/testthing/testthing.ts

Line 240 in 82f7f7a

checkActionInvocation("void-void", "undefined", typeof (await parameters.value()));

As no data schema is needed for an action with no output, calling value() on the interaction output throws an error. However, this behavior seems a little counterintuitive. I would think, intuitively, that an action without an output DataSchema would either provide no InteractionOutput at all or would provide and InteractionOutput with a value() method that resolves with undefined and an arrayBuffer() method that resolves with an empty array (maybe also undefined but it makes more sense you would actually get an array, but it's empty because there is no output).

[danielpeintner]

We could look whether a schema is available at all

node-wot/packages/core/src/interaction-output.ts

Line 94 in 82f7f7a

if (this.schema == null || this.schema.type == null) {

Hence, we should not do anything if this.schema == null and return undefined in such a case?

@relu91 @JKRhb any opinion?

[danielpeintner]

I created draft PR #1230 to show what I mean...

[FadySalama]

Throwing an error if schema.type == null will throw in cases in which the schema is correctly defined using "oneof"

[egekorkan]

Throwing an error if schema.type == null will throw in cases in which the schema is correctly defined using "oneof"

Related to w3c/wot-scripting-api#534

[relu91]

I think this is also related to satellite discussions: w3c/wot-thing-description#1234 and in particular w3c/wot-thing-description#1441. My opinion here is that the implementation is still correct, but we are lacking a way to clearly express the fact that we are expecting an empty payload.